Background and Objectives: Acute resistance exercise (RE) reduces vagal modulation and increases sympathovagal balance, which increases the risk for arrythmias. Few studies have examined sex differences in autonomic modulation after acute RE. The purpose of this investigation was to examine sex-specific responses to acute RE on autonomic modulation. Materials and Methods: Twenty-one resistance-trained individuals (men n = 11, women n = 10) between the ages of 19 and 25 y were analyzed for autonomic modulation in response to acute RE and a control (CON). Measures of autonomic modulation were collected at rest, 15 (R15), and 30 (R30) min following both conditions. Heart rate (HR), log transformed root mean square of successive differences (lnRMSSD), total power (lnTP), low-frequency power (lnLF), high-frequency power (lnHF), sample entropy (SampEn), and Lempel-Ziv entropy (LZEn) were measured at all time points. A three-way repeated analysis of variance (ANOVA) was used to analyze sex (men, women) across condition (RE, CON) and time (Rest, R15, R30). Results: The results are similar for all heart rate variability (HRV) variables at rest for both conditions (RE, CON). SampEn was significantly higher in men compared to women at rest for both conditions (p = 0.03), with no differences in LZEn (p > 0.05). There were no significant (p > 0.05) three-way interactions on any variables. Condition by time interactions demonstrated that both sexes increase in HR (p = 0.0001) and lnLF/HF ratio (p = 0.001), but decreases in lnRMSSD (p = 0.0001), lnTP (p < 0.0001), lnLF (p < 0.0001), lnHF (p = 0.0001), and LZEn (p = 0.009) at R15 and R30 compared to rest following acute RE and were different from CON. Condition by time interaction (p = 0.017) demonstrated that SampEn was attenuated at R15 compared to rest, and the CON, but not R30 following acute RE. Conclusion: Although SampEn is more complex at rest in men compared to women, autonomic modulation responses between sexes following acute RE appear to be similar.

The purpose of the study was to assess high-intensity battling rope exercise (HI-BRE) on hemodynamics, pulse wave reflection and arterial stiffness during recovery and between sexes. Twenty-three young, healthy resistance-trained individuals (men: n = 13; women: n = 10) were assessed for all measures at Rest, as well as 10-, 30-, and 60-minutes following HI-BRE. A one-way repeated measures ANOVA was used to analyze the effects of HI-BRE across time (Rest, 10, 30, and 60-minutes) on all dependent variables. Significant main effects were analyzed using paired t-tests with a Sidak correction factor. Significance was accepted a priori at p 0.05. There were significant reductions in hemodynamic measures of diastolic blood pressure (BP) in women, but not men following HI-BRE at 30 minutes. Further, measures of pulse wave reflection, specifically those of the augmentation index (AIx) and wasted left ventricular energy (ΔEw), were significantly increased in both men and women for 60 minutes, but changes were significantly attenuated in women suggesting less ventricular work. There were also significant increases in arterial stiffness in regard to the aorta and common carotid artery that were fully recovered by 30 and 60 minutes, respectively with no differences between men and women. Thus, the primary findings of this study suggest that measures of hemodynamics and pulse wave reflection are collectively altered for at least 60 minutes following HI-BRE, with women having attenuated responses compared to men.

Studies have reported gender differences in electrocardiographic (ECG) recordings. Specifically, females are reported to have higher heart rates (HR), shorter PR intervals, longer QT intervals, lower ECG voltages, ST segment deviations, and a greater prevalence of sinus arrhythmia. Yet, many studies report the need for more research on differences in ECG recordings in male and females. PURPOSE: To examine whether there are significant gender differences in ECG recordings. METHODS: A total of 104 active participants, including 34 male (M, age = 24.6 ± 10.3 yrs) and 70 females (F, age = 26.6 ± 12.2 yrs) were included in this study. Participants were excluded from the study if they had a positive disease history or if they indicated use of any medication that is reported to effect cardiac conduction. A standard 12-lead ECG was recorded after 5 minutes of supine rest. ANOVA was used to test for a significant effect of gender on heart rate (HR), PR interval, QTc interval, P axis, QRS axis, T axis, QRS/T Angle and on voltage criteria for left ventricular hypertrophy (LVH) based on the Cornell product (CP) and Sokolow-Lyon (SL). RESULTS: Significant differences between M and F subjects were found for HR (

Augmentation index (AIx) is derived from pressures imposed on the left ventricle as a result of systolic peripheral wave reflection. Differences in AIx in response to an acute stress, such as exercise, may prove useful for predicting future cardiovascular risk in younger adults, but less is known about whether this response differs between men and women. PURPOSE: To examine whether there are sex differences in AIx in response to an acute bout of exercise in healthy individuals. METHODS: Apparently healthy recreationally active individuals (18-42 yrs old; 10 men and 11 women) arrived at the lab 12 hrs fasted. Baseline measurements for AIx were taken using cuffbased applanation tonometry on the dominant arm. Participants underwent four rounds of dynamic body weight exercises. AIx measures were repeated at 5-, 10-, and 15-minutes post exercise and again 24-hrs post exercise. All AIx values were normalized to a heart rate of 75 bpm (AIx75). RESULTS: AIx75 was significantly higher in women (5.9 ± 3.6%) compared to men (-3.9 ± 2.6%) at baseline (P=0.04). Compared to baseline there was a significant increase in AIx75 in men (13.6 ± 3%; P<0.001) and women (26.2 ± 3.9%; P<0.001) 5-min post exercise with women exhibiting a significantly greater response (P=0.02). Compared to values at 5-min post exercise, there was a significant drop in AIx75 at both 10-min (18.6 ± 3.6%; P<0.001) and 15-min (15 ± 3.6%; P<0.001) post-exercise in women. However, AIx75 remained elevated in men at both 10min (16 ± 3.4%; P=0.33) and 15-min post exercise (12 ± 3.2%; P=0.1). Differences between sexes were not evident at either 10-or 15-min post exercise (P=0.58 and P=0.51, respectively). AIx75 returned to baseline levels at the 24-hr visit (P=0.57 for both men and women) and resting sex differences were again apparent (-5.5 ± 3.5% in men vs. 7.2 ± 3.5% in women; P=0.01). CONCLUSIONS: This study demonstrates sex differences in resting and post-exercise induced increases in AIx75. These findings suggest potential physiological or structural differences in women that are influencing arterial and left ventricular pressures at rest and in response to exercise.

Supramaximal interval exercise alters measures of autonomic modulation, while a cool-down may speed the recovery of vagal modulation. The purpose of this study was to compare the effects of a cool-down (pedaling a cycle ergometer at 50 rpm against a resistance of 45 W) versus passive recovery (no pedaling) after supramaximal interval exercise on autonomic modulation. Sixteen moderately active individuals (Mean ± SD: 23 ± 3 years (men: n = 10; women: n = 6) were assessed for autonomic modulation at Rest, and 15 (R15), 30 (R30), 45 (R45) and 60 (R60) min following supramaximal interval exercise. Linear measures of autonomic modulation included natural log (ln) total power (lnTP), high-frequency power (lnHF), the ratio of low frequency (LF) to HF ln(LF/HF) ratio, root mean square of successive differences between normal heartbeats (lnRMSSD), while non-linear measures included sample entropy (SampEn) and Lempel–Ziv entropy (LZEn). Two-way repeated ANOVAs were used to evaluate the main effects of condition (cool-down, passive recovery) across time (Rest, and R15, R30, R45 and R60). There were significant (p ≤ 0.05) condition by time interactions for SampEn and LZEn, such that they decreased at 15, 30, 45 and 60 min during passive recovery compared to Rest, with the recovery of SampEn and LZEn by 60 and 45 min, respectively, during cool-down. There were significant (p ≤ 0.05) main effects of time for lnTP, lnHF and lnRMSSD, such that lnTP, lnHF and lnRMSSD were attenuated, and lnLF/HF ratio was augmented, at all recovery times compared to Rest. These data demonstrate that a cool-down increases the recovery of nonlinear measures of vagal modulation within 45–60 min after supramaximal interval exercise, compared to passive recovery in moderately active individuals.

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